Ch 3-2

Ch 3-2

Energy Transformations and Work

The amount of net work done can be calculated using the following equation.

• Final Energy - Initial Energy = Work Done

• Example: A bicycle was has an initial energy of zero.  It accelerated and now 125 joules of energy.

• 125 ( Final Energy ) - 0 (starting energy) = 125 Joules

Work is defined as applying a force to an object to move it in a direction.

• If the object does not move then no work is done!

• Work is measured in joules (just like energy!)

Energy is the ability for an object to do work.

• Energy is measured using joules (J)

• There are multiple types of energy. We will talk more about the types later.

Multiple Choice

Staircase is a machine? What type of this machine?

• A pulley

• A lever

• An inclined plane

Multiple Choice

Which picture shows a lever?

Multiple Choice

Which picture shows a pulley?

Multiple Choice

A lever is a stiff bar that rests on a support (fulcrum). A lever is used to lift and move things. When you push down on one end, the other end lift up.

Which picture below shows a lever?

Multiple Choice

An inclined plane, or a ramp is a slanted surfaces. It connects a lower level to a higher level.

Which picture below shows an inclined plane?

Multiple Choice

What form of energy does a compressed spring have?

• heat energy

• kinetic energy

• chemical energy

• potential energy

Multiple Choice

When gasoline is burned in a car engine, ________ energy is converted into _________ energy.

• heat, chemical

• chemical, potential

• mechanical, chemical

• chemical, mechanical

Multiple Choice

How does the mass of a bowling ball that has been rolled down the lane affect the kinetic energy?

• The kinetic energy does not depend on the mass of the bowling ball.

• The kinetic energy is increasing proportional to the mass of the bowling ball.

• The kinetic energy is decreasing proportional to the mass of the bowling ball.

• The kinetic energy is increasing proportional to the square of the mass of the bowling ball.

Multiple Choice

Which of the following best represents the Law of Conservation of Energy?

• Energy CAN be created but NOT destroyed

• Energy CAN be destroyed but NOT created

• Energy can NOT be created Nor destroyed

• Energy CAN be created and CAN destroyed

Multiple Choice

Which of the following statements is not correct?

• Energy is the capacity to do work.

• Work can be expressed as force × displacement

• Unit of work done is joule.

• Unit of energy is Newton

Multiple Choice

The capacity to do work is called ___________.

• acceleration

• power

• energy

• pressure

Multiple Choice

The work done by a body is the product of force and

• distance.

• displacement.

• speed.

• velocity.

Multiple Choice

Work can be _____________.

• positive only

• negative only

• either positive or negative

• neither positive nor negative

Multiple Choice

Work done =

• $F\times d$

• Fm

• $\frac{F}{d}$

• FG

Multiple Choice

Work is calculated by taking the __________ in final and initial energy.

• Sum

• Difference

• Square Root

• Product

Multiple Choice

Jeremias pushed on a car with all of his might, but it did not move. Did he do any work?

• Yes

• No

Multiple Choice

What two things must occur for work to be done?

• Force and Energy

• Energy and Movement

• Force and movement

Multiple Choice

Energy is the ability to do work.

• True

• False

Multiple Choice

When electric current passes through an electric bulb, electric energy is converted to

• Heat energy only

• light energy only

• both heat and light energy

• both light and chemical energy

Multiple Choice

Potential energy of a stretched string is

• Gravitational P.E.

• Plastic P.E.

• Elastic P.E.

• None of these

Multiple Choice

Water stored in a dam possesses

• Kinetic energy

• Potential energy

• Electric energy

• no energy

Multiple Choice

S.I. unit of energy is

• erg

• dyne

• joule

• newton

Multiple Choice

In a tug of war, work done by losing team is

• zero

• positive

• negative

• none of these

Multiple Choice

Work is done on a body when

• force acts on the body but not displaced

• force does not act on the body but it is displaced

• force acts on the body perpendicular to the direction of displacement of body

• force act on a body and the displacement is in direction of force or opposite to direction of force

Multiple Choice

Which of the following shows the correct order of the energy transformations that occur when green plants produce their food from the Sun’s energy?

• chemical → thermal
• light → chemical
• thermal → light
• chemical → electrical

Multiple Choice

A lamp that plugs into a wall socket draws energy which flows through a thin wire in the bulb causing it to glow. What energy transformations are taking place?

• chemical → light → electrical
• mechanical → sound → light
• thermal → solar → electrical
• electrical → thermal → light

Multiple Choice

Which type of energy transformation occurs when a flashlight shines?

• chemical → thermal → electrical
• chemical → electrical → light
• thermal → chemical → light
• chemical → electrical → chemical

Multiple Choice

Which of the following chemical energy to radiant energy?

• solar calculator
• windmill
• glow stick
• firecracker

Multiple Choice

Which of the following radiant energy to electrical energy?

• solar calculator
• windmill
• glow stick
• firecracker

Multiple Choice

What is the best example of a device that converts electrical energy to light and sound?

• a clock radio
• a toaster
• a flashlight
• an electric toothbrush

Multiple Choice

What is the best example of a device that converts electrical energy to thermal energy?

• a toaster
• a clock radio
• a flashlight
• an electric toothbrush

Multiple Choice

During most energy transformations and transfers, wasted energy takes the form of __.

• electromagnetic radiation
• sound waves
• random mechanical movements
• heat

Multiple Choice

What kind of energy transformation takes place in this system?

• chemical to electrical to light
• electrical to chemical to light
• electrical to light to chemical
• light to chemical to electrical

Multiple Choice

In energy transformations, "wasted energy" usually takes what form?

• heat
• chemical energy
• light
• sound waves

Multiple Choice

Which of the following energy transfers occurs when food is digested?

• chemical to mechanical

• radiant to nuclear

• mechanical to potential

• thermal to chemical

Multiple Choice

Turning on a lamp is an example of energy transformation from electrical to 3 forms of energy. Which of these is NOT created by the lamp?

• radiant

• light

• heat

• chemical

Multiple Choice

What best describes the energy conversion that takes place in a microwave oven?

• electrical to light to thermal

• chemical to thermal to light

• electrical to thermal to sound

• nuclear to thermal to chemical

Multiple Choice

What is the best example of a machine that converts electrical energy into kinetic energy and sound energy?

• an electric toothbrush

• a toaster

• a flashlight

• an iron

Multiple Choice

What is the best example of a machine that converts electrical energy into kinetic energy and sound energy?

• an electric toothbrush

• a toaster

• a flashlight

• an iron